Folding ladder and shiftable platform for floating type tank roofs



Feb. 15, 1944. J, H, New 2,341,890

TYPBTANK ROOFS FOLDING LADDER AND SHIFTABLE PLATFORM FOR FLOATING Filed on. 'r. 1942 2 Sheets-Sheet 1 JOHN H. n; ms M C A TTORNEY Feb. 15, 1944. J. H. WIGGINS FOLDING LADDER AND SHIFTABLE PLATFORM FOR FLOATING TYPE TANK ROOFS Filed Oct. 7. 1942 2 Sheets-Sheet 2 FIGZ.

. JbH/v H. W/ ems ATTORNEY Patented Feb. 15, 1944 FOLDING LADDER sun smr'rssns rur- FORM roa FLOATING ms TANK noose John n. Wlllna, Chicago, 111. Application 0mmr, 1942, Serial No. 401,220 9 Claims. (0!. 228-1) This invention relates to ladders or stairs oi the kind that are used with floating type tank roots to provide access to the root when it is located at the bottom of the tank and when it isfloating on theliquidinthetank.

One object or my invention is to provide a strong, light-weight floating tank root ladder that is or simple design, easy to erect, convenient to use, and of inexpensive construction.

Another objectis to provide a floating root ladder that has suflicient stillness or rigidity to prevent it from flexing or swaying from its own weight or the added weight of a person using same, and which is or such desisn or construction that the portion oi! same disposed between the root and the top edge or the side wall of the tank will maintain approximately the same slope or angle during the maior portion or the vertical travel 0! the rooi. Another object is to provide a ladder or stair tor floating tank roots, that will not impose an objectionable or excessive load on the root, or subject the root to thrusts or strains tending to rotate the root or hit or tilt it Another object is to provide a floating root storage tank, that is equipped with a novel ladder provided with a hand rail, and a platform disposedatthetop edgeoithesidewalloithetank in overhanging relation with the root so as to provide easy access to the root ladder, said platform being constructed so that it will shii't automatically into an inactive position, and thus not strike asainst the side wall seal or other parts carried by the roof, when the root approaches its extreme elevated position.

And still another object of my invention is to provide a novel way of counterbalancing a ladder or stair tor floating tank roots. Other objects and desirable ieatures or my invention will be hereinafter pointed out.

ment of the roof, the upper portion of the ladder folds, preferably downwardly and outwardly over the top edse oi the side wall 01' the tank and assumes an inactive position on the exterior or the tank. During the downward movement or the root, the portion or the ladder on the exterior oi the tank which previousLv had i'olded, will unfold and assume an active or operative position on the interior oi the tank so as to constitute a. rigid trussed ladder. disposed between the roof and the top edge oi the side wall 01' the tank.

In order to prevent the ladder from imposing an excessive or objectionable load on the root. or subjecting the root to thrusts or strains tending to rotate the root or tilt or hit it, I have equipped the ladder with a counterbalancing mechanism which is prei'erably constructed in such a manner that the iolded portion oi the ladder on the exterior or the tank, is utilized as a load to assist in counterweishting the rigid portion or the ladder disposed on the interior of the tank between the root and the top edge 01' the side wall of the tank. The speciflc construction of the co-acting sections of the ladder is immaterial so is:- as my broad idea is concerned, but I prefer to use ladder sections 01' girder construction, ivotally connected together insuchawaythatwhentheyaredisposedin longitudinal alignment with each other, they form a trussed ladder that is equipped with a hand rail and which has sufllcient rigidity both longitudinally and transversely to prevent it from flexing or buckling, notwithstanding the fact that it is or relatively great length.

l igureloi'thedrawingsisatragmentary. vertical transverse sectional view through the tank, showing the ladder in side elevation and the floating root arranged adjacent the bottom or thetank. the platforms and associated parts being omitted Figure 2 is a top plan view showing the ladder, the wheel, the shiitable platform. the stationary platform and the outside stairway leading to the stationary platform.

Figure 3 is a iragmentary side elevational view,

showingindottedlineshowtheshittahleplatform tilts upwardly so as to not interfere with thesidewailsealorotherpartscarriedbythe floating root. when the root approaches its extremeelevatedposition.

sureiisatraversesectionalviemtaken 'through'one oithesectlomoitheladder; and

Fllllre5isadetlllpllnm,mllstraflnltbe constructionoithesuidescntheladdersostions that prevent the top chord members or hand rail members of said sections from moving laterally relatively to each other.

In the accompanying drawings which illustrate the preferred form of my invention, A designates the side wall of a tank or container that is adapted to be used for storing oil or other liquid, B designates a floating roof that floats on the liquid in the tank, designates a ladder or stair mounted on the top side of the roof and supp rted in an upright, sloping or inclined position by the side wall of the tank, D designates a stationary platform (see Figure 2) mounted on the exterior of the side wall of the tank and projecting outwardly from the top edge portion of same, E designates a shiftable platform arranged alongside of said stationary platform and projecting inwardly into the tank in overhanging relationship with the roof B, so as to provide easy access to the ladder, and F designates a wheel or reel mounted on the exterior of the side wall A of the tank at the top edge of same, as shown in Figure 1, so as to form a rotatable bearing over which the pivotally connected sections of the lad,- der C move when said ladder folds and unfolds during the rise and fall of the roof B, said wheel or reel F being of any preferred cross-sectional shape and mounted in any preferred manner on the tank side wall.

The ladder C is composed of a plurality of truss sections l, comprising bottom chord members pivotally connected together at 2 and top chord members or hand rail members constructed so that they are eifectively held against relative rocking movementin one direction, but are free to separate and rock relatively to each other in the opposite direction. when said truss sections l are in longitudinal alignment with each other, the adjacent ends of the top chord members or hand rail members of said sections are in abutting relationship, and hence, co-act with each other to produce a rigid ladder that extends upwardly from the roof to the top edge of the side wall of the tank, as shown in Figure 1. The lower end of the ladder C is pivotally connected to the roof B, or is rockably mounted in hearings on said roof, and the upper end of said ladder has attached to same pivotally connected links or flexible devices 8 that lead over the reel F and carry a counterweight 4. Accordingly, during the upward movement of the roof, the truss sections i of the ladder rock relatively to each other in such a manner that the ladder will fold over the wheel F and hang suspended from said wheel on the exterior of the tank, as shown in broken lines in Figure 1, and during the down ward movement of the roof said ladder sections will unfold progressively and move into longitudinal alignment with each other with the adiacent ends of the hand rail members in abutting relation so as to form a trussed ladder on the interior of the tank that is perfectly rigid, even when the roof is in its lowermost position at the bottom of the tank.

The counterweight l exerts a sufficient upward Pull on the ladder C when the roof B is in its extreme low position, to prevent said ladder from imposing an excessive load on the roof. as the ladder rises, due to the upward movement of the roof, the counterbalanclng eflect produced by the counterweight I first becomes less, due to the change in the position of the links I that carry said counterweight, and then becomes greater, due to the added weight of the folded sections of the ladder that have moved downwardly over the wheel F and the reduction in weight of the rigid or unfolded portion of the ladder located inside of the tank between the wheel F and the roof B. This eflect would eventually become so great as to create too large a lift on the roof. which would be objectionable, cause it would tend to affect gaging the liquid contents of the tank, and might also create a radial pull on the roof, tending to pull the roof of! center. Therefore, I attach the counterweight l to one end of a chain or flexible element 5. whose opposite end is attached to a stationary part on the tank side wall, said chain i being of such length that the counterweight 4 will hang on said chain under certain conditions. For example, when the counterbaiancing effect becomes a certain amount, the counterweight l itself is picked up by the chain 5. At this point the rigid or unfolded portion of the ladder on the inside of the tank may actually change from, say a hundred pound pull to a hundred pound load,

but as the roof B rises higher, this load reaches zero and then goes into a pull on the roof again. By the means above described, I keep the pressure or tension produced on the roof by the ladder, to a minimum; and another desirable characteristic of said means is that it insures that the radial pulls and pushes on the roof will be small and alternate, thus tending to prevent the roof from being pulled of! center. Obvious y. other counterbalancing means or devices than the one above described could be used, without departing from the spirit of my invention.

The specific construction of the truss sections l of the ladder C is immaterial, so far as my broad idea is concerned. I prefer, however, to use truss sections of girder construction, each of which comprises two bottom chords 8 that carry rungs or foot treads 6, two top chords I that constitute portions of hand rails, and struts or uprights 8 that connect together the top and bottom chords at each side of the ladder. At one end of each ladder section flared guides 9 are attached to the top chord members or hand rail members 1, so as to guide the adjacent ends of said hand rail members into proper abutting relationship, during the downward movement of the roof and also to prevent relative lateral movement of the adjacent ends of said hand rail members. The guides 9 also co-act with the hand rail members I to produce continuous hand rails, which help to counter side sway and toresist forces applied to the ladder in a direction circumferentialiy of the tank. If desired, the truss sections of the ladder can also be provided with inclined braces III, as shown in Figure 4, to aid in this result. In a ladder of the design above described, each of the sections l is a still truss in itself. and when said sections .are disposed in longitudinal alignment with each other with the ends of the top chord members I in abutting or interlocked relationship, they produce a stiff, ri id ladder extending downwardly from the top edge of the tank side wall to the roof, which an operator can use with perfect safety, due to the fact that it will not flex, swing, or sway. Another very desirable feature of the ladder and counter-balancing mechanism above described, is that they are inexpensive to construct, easy to install, and contain less metal, and are. lighter in weight than floating roof ladders of conventional design.

Access to the stationary platform D is afforded byastationary stairwayDleadingfi-omthe ground. on the exterior of the tank. as chm arable abutting relationship, and struts or upin Figure 2. The hift-able platform that prorights which rigidly :Iects into the tank in overhanging relationship ing members of said top and bottom chords. with the floating roof, may be of any preferred 3. A liquid storage tank provided with a floatconstruction, so long as it is of such design that ing roof, a Jointed or foldable ladder mounted in it will shift automatically into an inactive posian inclined position on said roof, a device at the tion. and thus not interfere with the side wall top edge of the tank side wall over which the seal or otherparts carried by the floating roof, upper portion of the ladder folds and han s in when the roof moves into its extreme elevated poa suspended condition on the exterior or the sition. In the preferred form of my invention tank side wall when the roof moves upwardly, herein illustrated the outer end of the platform m and a hand rail structure that imparts rigidity E rocks on a horizonta -disposed pivot or bearto the portion of the ladder disposed between ing H, shown in Figure 2, and the floating roof the roof and the device at the top edge of the B is provided at its peripheral portion with a side wall over which the ladder folds, said hand wheel or equivalent part 12, disposed so that as rail structure comprising longitudinally-aligned said roof approaches its extreme elevated posip top chord members connected by struts with the tion, the wheel I! will engage the platform E rung or tread carrying members of the ladder and tilt it upwardly, as shown in broken lines and disposed with their ends in separable abutin Figure 3, out of the way of any of the parts ting relationship. on the roof which might be damaged by striking a. A liquid storage tank provided with a floatagainst the platform E. ing roof, an inclined ladder rockably mounted on A floating tank roof ladder of the construction said roof and support y the t side wall. above described is desirable, in that it never asand a means at the top edge of said side wall sumes an angle that makes it difficult for the over which the upp Portion f e ladder folds user to traverse same; it is perfectly rigid and and hangs suspended on the exterior of the tank has no tendency to sway when a person is using when the roof moves p y. 581d ladder the same to reach the roof or leave the roof; it prising a series f to chord members pivo has continuous hand rails which can be gras ed ally connected together, ri id s r t-s or sheer easily by the user's hands; it reduces the time members Said bfltwm chOId member5,and required to pass onto or of! of the roof wh chord members rigidly combined with said struts the roof is located in an intermediate position a d arran d in s p ra abutting relationship.

5. ing roof, an inclined ladder rockably mounted on said roof and supported by the tank side wall, a means at the top edge of said side wall over which the upper portion of the ladder folds and hangs suspended on the exterior of the tank when the roof move upwardly, said ladder comprising a series of bottom chord members pivotally connected together, rigid struts or shear members on said chord members, and a series of hand rail members having no direct connection with each or elevated position, due to the fact that at such times the rigid portion of the ladder located on the interior of the tank comprises fewer rungs or foot treads; objectionable loads or strains on the roof that proper functioning of the root; onto or off of, notwithstanding the fact that it is equipped with hand rails due to the fact that it is disposed at one side of a platform on the side wall of the tank which projects into the tank in overhanging relationship with the floating 85 it is easy to step i roof; and it is light in weight, inexpensive to oonother but adapted to move into abutting relationstruct, and easy to install. ship with each other so as to co-operate with said Having thus described my invention, what I bottom chord members and struts to iorm a trussed ladder.

6. A liquid storage tank provided with a floating roof, a trussed ladder mounted in an inclined position on the roof with its weight sustained by the tank side wall, said ladder comprising bottom chords formed by two series of rung or tread carrying members pivotally connected together and top chords formed by two series of hand rail members arranged in separable abutting relationship, a shiftable platform on the tank side wall arranged adjacent said ladder in overhanging relationship with the roof, and means on the roof that moves said platform into an inactive position when the roof approaches its extreme elevated position.

claim as new and desire to secure by Letters Patout is:

l. A liquid storage tank provided with a floating roof, a Jointed or foldable ladder mounted inclined position and extendprovision for enabllng it to fold outwardly and downwardly over the top wall when the roof moves rail combined with said ladder so as to constitute the top chord of a truss which imparihrigidity disposed between tank side wall, said hand rail being longitudinallyaligned members in abutting relationship, that are capable of completely separating or pulling apart when the ladder folds outwardly and downwardly over the tank side wall.

2. A liquid storage tank provided with a float ing roof, a jointed or foldable ladder disposed in an inclined position on the roof, and a means at the top edge of the side wall of the tank over which a portion of said ladder folds outwardly and downwardly when the roof rises, said ladder being composedof two parallel side trusses, each or which comprises a bottom chord formed by a plurality of rung or tread carrying members whose ends are pivotally connected together, a top chord formed by an equal number of hand rail members whose ends are arranged in seping roof, a jointed or on said roof in an ing upwardly from same, said ladder comprising pivotally connected rung or tread carrying memhere that are capable of rocking or moving relatively to each other so as to permit the ladder to fold outwardly and downwardly over the top edge of the tank side wall when the roof moves upwardly, and means for imparting rigidity to the portion of the ladder disposed between the roof and the top edge of the tank side wall, consisting of longitudinally-aligned, abutting hand rail members rididly combined with the rung or tread carrying members and adapted to move out of abutting relationship with each other as said tank provided with a floatconnect together correspondrungcaxryingmemb'ersfoldoverthetopedge thetankaldewall.

8. AliqlliditOmBBh-Ilk 9.1 nqmd mm mm: provided with a float- JOHN H. WIGGINS. 

